This invention relates to a document handling system and, more particularly, to a dual purpose document handling system for a reproducing machine in which the original documents may be conveyed across the platen at a constant or synchronized speed or fed to the platen at a high speed.
Document handling systems have previously been employed in reproducing machines, such as xerographic machines, for conveying original documents relative to a window or platen at which they are viewed and imaged for reproduction. One such machine includes an endless belt conveyor which delivers the original document to be copied at high speed onto the viewing platen where the document is positioned for copying by suitable registration gates. Once the document is registered, the conveyor is stopped and the number of copies desired are made. When copying of the given original document is completed, the registration gates are retracted and the document is driven from the platen by the high speed belts and a new document is delivered into position on the platen for copying. In such document handling systems, the original document is stationary on the platen during copying and the optics of the xerographic machine usually move so as to scan the stationary document during imaging.
The advantage of such fixed document-moving optics systems are severalfold. In the first instance, such reproducing machines are generally capable of higher throughput, particularly where multiple copies are desired, since the document is delivered to the platen at high speed and the next document is delivered for copying while the first document is being removed and the moving optics are returning to the start position. Additionally, the original need not be moved between multiple copies and, thereby, the time between copies is a function of the speed of the xerographic machine itself, e.g. the speed at which the moving optics returns to the start position. Moreover, such machines have the advantage of consistent quality between multiple copies, since the original document is held in the same stationary position for all copies.
The disadvantages of such fixed document-moving optics systems are also severalfold. Such machines are capable of completely reproducing only a fixed range of original document sizes. The operator must select the document size prior to copying the document from one of a limited number of selections. Thus, the reproduction of oversized non-standard dimension original documents is difficult or impossible without patching of the copy.
Another form of machine comprises a similar endless belt conveyor for conveying the original documents across the platen. However, in this machine the speed at which the original document is conveyed across the platen is maintained at a relatively predetermined constant speed which is a function of the speed of the photoreceptor drum of the xerographic machine. In this document handling system, the optics are fixed and the original document is conveyed across the platen at this constant speed and only a small portion of the original document is viewed at any given time by the fixed optics as the document moves past the optics, thus, resulting in the scanning otherwise accomplished in the stationary document-moving optics system. This second form of document handling system is thereby referred to as a moving document-fixed optics system.
The latter system also has several advantages. One advantage is that the relatively elaborate mechanisms needed to drive the optics at a predetermined speed are no longer necessary, since the optics are stationary. Moreover, the copying of oversized original documents is facilitated, since the length of the document is no longer relevant.
The principal disadvantage of such moving document-fixed optics machines are their relatively low copying speed, particularly where multiple copies are desired. Moreover, since the original document must be fed across the platen each time another copy is to be made, handling and recycling mechanisms which are relatively complicated are necessary and consistency in quality between multiple copies is reduced.
The present invention relates to a dual purpose document handling system which is capable of operation in both the fixed document-moving optics and moving document-fixed optics modes. Thus, the document handling system of the present invention realizes the advantages of both the fixed document-moving optics and moving document-fixed optics systems and avoids substantially all of their respective disadvantages.
In the system of the present invention the speed of the moving document in the moving document-fixed optics mode is capable of accurate control thereby resulting in close synchronization of the speed of the document with the speed of the photoreceptor. Such accurate speed synchronization results in copies which are clear and accurate. Moreover, the dual purpose document handling system of the present invention is capable of performing in both aforementioned modes, and yet, is compact and duplication of parts is minimized.
In a system incorporating the principles of the present invention, support means supports individual documents in a position in which work may be performed relative to the documents, and document conveyor means conveys the documents relative to this position. Drive means drives the conveyor means to convey the documents at a constant speed to and through this position or, in the alternative, at a greater speed to the position. Selector means controls the document conveyor means to drive the individual documents at the constant speed or at the greater speed.
In another aspect of the present invention, the document handling system is incorporated in a document reproducing machine and the support means comprises an optical exposure station of the reproducing machine. A copy processing section includes photoreceptor means for transferring images to a copy sheet, drive means for driving the photoreceptor means at a substantially constant speed, and sensing and control means is located between the document conveyor means and the photoreceptor means for sensing the speed of the latter to control the document conveyor means and synchronize the speed of the document conveyor means and the speed to the photoreceptor means.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description: